High-frequency signaling



Jan. 1925. 1,523,139

v E. PETERSON HIGH FREQUENCY SIGNALING Filed Dec. 15, 1923 m 5/ my den. 13, W25.

EUGENE PET 0N, OF NEW YORK, H. Ti, ASfiIGNOR. Ti) WTERN ELECTRIC COM- PANY, IN ORPORATEB, OF NEWYORK, N. iii, A CORPORATION OF NEW YORK.

HIGH-FREQUENCY SIGNALING.

Application filed December 15,- ieas. Serial no. esasu.

To all whom it may concern:

Be it known that I, EUGENE PETERSON, a citizen of the United States of America, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Hi h-Frequenc Signaling, of which the to owing 1s a ull, clear, concise, and exact description.

This invention relates to high frequency signaling and particularly to high frequency transmission systems.

It is an ob'ect of the invention to produce ecient and improved modulation of a high frequency or carrier wave in accordance with a signal or other control wave.

Briefly, the invention relates to a transmission system in which a, high frequency carrier wave is modulated in accordance with signal currents such. as waves of speech frequency, thereby giving the high frequency oscillations a s eech signal wave form. In such systems it is customary to suppress part ofthe products of modulation, as for example, one side-band, or the unmodulated carrier and one of the side hands, by means i of a wave filter, passing only the remaining rtions of the wave to the high frequency ine. At the distant station the received signal may then be recast into intelligible form by a suitable demodulating apparatus. A di cultv is encountered in transmission sys of the above type however, in that a relative variation in eit er the filter constants or in the, tuning elements of the oscillator shifts the portion of the wave that is suppd and causes a confusion of the. transmitted wave. This dificulty is overcome by the present invention.

In accordance with a feature of the invention, means is provided for trans mitting a uniform modulated wave irres ective of relative variations in either the ter constants or the tuned oscillatory circuit.

This is accomplished by the provision of means whereby a variation in the filter con stants produces a corresponding change in the transmitted side bano so that the some portion of the modulated wave is tranmnitted at all times.

More specifically, the invention provides a modulator in which the usual tuning co denser of the oscillatory circuit is replaced by the capacity included in a filter which ,a speech serves both for selecting the side band and also to determine the frequency of the oscillator. In this system, a change in the filter constants such as to cause a change in the frequency of the oscillations, and consequently 1n the frequency of the modulated Wave, also causes a corresponding change in the transmission range of the filter.

The invention is illustrated in connection with a modulator of the coupled plate or socalled constant current type comprising an oscillator preferably consisting of a vacuum tube of the audion t pe connected to an 0scillatory circuit, and voltage supplied to the oscillator in accordance with audio-frequency oscillations. The means for varying the voltage supply of the oscillator may consist of a vacuiun tube of the audion type on whose input terminals the audio-frequency signals are impressed, the resultant amplified signals in the output circuit being impressed on the output circuit of the oscillating tube, thereby givin to the high frequency oscillations a space signal wave form. Certain of the modulation components may-be suppressed in the band filter which also furnishesthe capacity of the oscillatory circuit, and the side band which it is desired to transmit may then be impressed on the transmitting terminals of a high frequency line circuit or, in the case of radio transmission, on a wireless antenna.

The drawing shows a diagrammatic illustration of a carrier transmission system embodying the invention.

Referring to the drawing, a microphone 1, representing an ordinary subscribers telephone transmitter or any other low frequency transmitting device, is connected to frequency line 2. The line 2 is coupled by means of a transformer 3 to the input of a vacuum tube a of the audion t pe. Plate 5 of this tube is connected t rou h an anti-resonant circuit 6 with the plate of an oscillator tube 8. S ace current is furnished for both tubes cm the source 9 through choke coil 10, which is designed to Oder high impedance to the passage therethrough of currents of speech frequencies or higher quencies. The input circuit of the oscillator tube 8 includes a coil 11 which is connected between the cathode l2 and control element 13 of this tuhe. A. grid lealr M and a hloclring condenser l5 are also included in this circuit.

means for varying the lllil) The coil 11 in the input circuit of the oscillator tube 8 is inductively related to the coil 16 which, together with the capacity.

tuned tothe frequency of the carrier wave generated by the oscillator and consequently the carrier will not be passed to the speech amplifier tube 4. There is a speech frequency path from the plate circuit of the speech amplifier tube 4, however, to the oscillator tube, and consequently the speech currents amplified in the tube 4 are impressed on the output circuit of the oscillator tube 8 to modulate the carrier wave.

The filter 17 while serving to determine the frequency of the oscillator may, at the 95 of the products of modulation and to pass othersto the line for transmission to a distant station, not shown. Heretofore, since the filter for suppressing part of the modulated wave and the tuning elements for the oscillator have been separate units, a relative variation in either the filter constants or the tuning would shift the portion of the wave to be suppressed. According to the present invention, if there is a variation 105 in the oscillator frequency due to changes in the filter constants, the transmitted band shifts accordingly so that the portion of the modulated wave transmitted remains the.

same. By means of this arrangement, the 110 filter 17 may be designed to have the proper capacity and proper impedance so that the frequency of the oscillator is maintained at a point near the edge of .the side band that is to be transmitted. This enables one 5 side band or one side band and the carrierto be suppressed and the other side-band with or without the carrier, to be transmitted. In a 'particular system employed by applicant. for a carrier frequency of 120 8000 cycles, the side band transmitted was 6000 to 8000 cycles. In this case, the inductance of the coil 16 was ,millhenrys and the capacity reactance of the filter 17 was so proportioned in accordance with the above mentioned Campbell patent as to resonate with the coil at the carrier frequency, while the filter passed selectively the band from 6000 to 8000 cycles, as mentioned above.

While for the purpose of illustration the same time, be adjusted to suppress certain.

invention has been described in connection with a carrier line signaling system, it will be understood that it is equally applicable to radio signaling systems.

The invention may also be embodied in forms other than that herein shown and described without departing in .any way from the spirit of the invention, the scope of which is defined in the appended claims.

What is claimed is:

1. In a signaling system, means for inde pendently generating two waves, means for modulating one of said waves in accordance with the other to produce side bands lying above and below the frequency of said modulated wave, and common means for controlling the frequency of the wave to be modulated and for suppressing the side band lying to one side of said wave.

2. In a signaling system, means for generating a high frequency wave, means for modulating said wavein accordance with audio-frequency currents to produce side bands lying above and below said high frequency wave, and a tuned circuit for said generator including means forsuppressing the side band lyin to one side of said wave.

3. In a signa mg system, means for modulating a high frequency wave in accordance with speech currents to produce side bands lying above and below the frequency of said wave, an oscillation generator, and common means for determining the frequency of said generator and for sup pressing the side band lying to one side of said. .Wave. I

a 4, In a signaling system, means for modulating a high frequency wave in accordance with speech currents, a generator of hi h frequency waves, and a filter in the oscil 21- tory circuit of said generator adapted to determine the frequency of said generator and to selectively transmit the products of modulation.

5. In a transmission system, means for modulating a high frequency wave in accordance with speech currents to produce side bands lying aboveand below the frequency of said wave, means for impressin currents of speech frequency upon sai modulating means, and means to determine the frequency of the wave to be modulated and to sup ress the side band lying to one side of said wave.

6. In a transmission system, means for modulating a high frequency wave in accordance with speech currents, a circuit for impressing currents of speech fr uency upon said modulating means, and a ter in the output of said system adapted to determine the frequency of the wave to be modulated and to selectively transmit the prodacts of modulation.

7. In a transmission of stem, a pair vacuum tubes having their plates coupled with the first mentioned tube adagteed to of one of said'tubes and speech frequency oscillations to the input circuit of the other tube, a common source of substantially constant current for supplying space current to said tubes, and a band filter associated determine the frequency of said tu and for selectively transmitting the product of the combined carrier and speech frequency currents. I

In witness whereof, I hereunto subscribe my name this 12 day of December A. D.,

EUGENE PETERSON. 

